// SPDX-License-Identifier: GPL-2.0-only
/*
 * Persistent Storage - ramfs parts.
 *
 * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/fsnotify.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/string.h>
#include <linux/mount.h>
#include <linux/seq_file.h>
#include <linux/ramfs.h>
#include <linux/parser.h>
#include <linux/sched.h>
#include <linux/magic.h>
#include <linux/pstore.h>
#include <linux/slab.h>
#include <linux/uaccess.h>

#include "internal.h"

#define PSTORE_NAMELEN  64

static DEFINE_MUTEX(records_list_lock);
static LIST_HEAD(records_list);

static DEFINE_MUTEX(pstore_sb_lock);
static struct super_block *pstore_sb;

struct pstore_private {
        struct list_head list;
        struct dentry *dentry;
        struct pstore_record *record;
        size_t total_size;
};

struct pstore_ftrace_seq_data {
        const void *ptr;
        size_t off;
        size_t size;
};

#define REC_SIZE sizeof(struct pstore_ftrace_record)

static void free_pstore_private(struct pstore_private *private)
{
        if (!private)
                return;
        if (private->record) {
                kfree(private->record->buf);
                kfree(private->record);
        }
        kfree(private);
}

static void *pstore_ftrace_seq_start(struct seq_file *s, loff_t *pos)
{
        struct pstore_private *ps = s->private;
        struct pstore_ftrace_seq_data *data;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (!data)
                return NULL;

        data->off = ps->total_size % REC_SIZE;
        data->off += *pos * REC_SIZE;
        if (data->off + REC_SIZE > ps->total_size) {
                kfree(data);
                return NULL;
        }

        return data;

}

static void pstore_ftrace_seq_stop(struct seq_file *s, void *v)
{
        kfree(v);
}

static void *pstore_ftrace_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
        struct pstore_private *ps = s->private;
        struct pstore_ftrace_seq_data *data = v;

        (*pos)++;
        data->off += REC_SIZE;
        if (data->off + REC_SIZE > ps->total_size)
                return NULL;

        return data;
}

static int pstore_ftrace_seq_show(struct seq_file *s, void *v)
{
        struct pstore_private *ps = s->private;
        struct pstore_ftrace_seq_data *data = v;
        struct pstore_ftrace_record *rec;

        if (!data)
                return 0;

        rec = (struct pstore_ftrace_record *)(ps->record->buf + data->off);

        seq_printf(s, "CPU:%d ts:%llu %08lx  %08lx  %ps <- %pS\n",
                   pstore_ftrace_decode_cpu(rec),
                   pstore_ftrace_read_timestamp(rec),
                   rec->ip, rec->parent_ip, (void *)rec->ip,
                   (void *)rec->parent_ip);

        return 0;
}

static const struct seq_operations pstore_ftrace_seq_ops = {
        .start  = pstore_ftrace_seq_start,
        .next   = pstore_ftrace_seq_next,
        .stop   = pstore_ftrace_seq_stop,
        .show   = pstore_ftrace_seq_show,
};

static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
                                                size_t count, loff_t *ppos)
{
        struct seq_file *sf = file->private_data;
        struct pstore_private *ps = sf->private;

        if (ps->record->type == PSTORE_TYPE_FTRACE)
                return seq_read(file, userbuf, count, ppos);
        return simple_read_from_buffer(userbuf, count, ppos,
                                       ps->record->buf, ps->total_size);
}

static int pstore_file_open(struct inode *inode, struct file *file)
{
        struct pstore_private *ps = inode->i_private;
        struct seq_file *sf;
        int err;
        const struct seq_operations *sops = NULL;

        if (ps->record->type == PSTORE_TYPE_FTRACE)
                sops = &pstore_ftrace_seq_ops;

        err = seq_open(file, sops);
        if (err < 0)
                return err;

        sf = file->private_data;
        sf->private = ps;

        return 0;
}

static loff_t pstore_file_llseek(struct file *file, loff_t off, int whence)
{
        struct seq_file *sf = file->private_data;

        if (sf->op)
                return seq_lseek(file, off, whence);
        return default_llseek(file, off, whence);
}

static const struct file_operations pstore_file_operations = {
        .open           = pstore_file_open,
        .read           = pstore_file_read,
        .llseek         = pstore_file_llseek,
        .release        = seq_release,
};

/*
 * When a file is unlinked from our file system we call the
 * platform driver to erase the record from persistent store.
 */
static int pstore_unlink(struct inode *dir, struct dentry *dentry)
{
        struct pstore_private *p = d_inode(dentry)->i_private;
        struct pstore_record *record = p->record;
        int rc = 0;

        if (!record->psi->erase)
                return -EPERM;

        /* Make sure we can't race while removing this file. */
        mutex_lock(&records_list_lock);
        if (!list_empty(&p->list))
                list_del_init(&p->list);
        else
                rc = -ENOENT;
        p->dentry = NULL;
        mutex_unlock(&records_list_lock);
        if (rc)
                return rc;

        mutex_lock(&record->psi->read_mutex);
        record->psi->erase(record);
        mutex_unlock(&record->psi->read_mutex);

        return simple_unlink(dir, dentry);
}

static void pstore_evict_inode(struct inode *inode)
{
        struct pstore_private   *p = inode->i_private;

        clear_inode(inode);
        free_pstore_private(p);
}

static const struct inode_operations pstore_dir_inode_operations = {
        .lookup         = simple_lookup,
        .unlink         = pstore_unlink,
};

static struct inode *pstore_get_inode(struct super_block *sb)
{
        struct inode *inode = new_inode(sb);
        if (inode) {
                inode->i_ino = get_next_ino();
                inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
        }
        return inode;
}

enum {
        Opt_kmsg_bytes, Opt_err
};

static const match_table_t tokens = {
        {Opt_kmsg_bytes, "kmsg_bytes=%u"},
        {Opt_err, NULL}
};

static void parse_options(char *options)
{
        char            *p;
        substring_t     args[MAX_OPT_ARGS];
        int             option;

        if (!options)
                return;

        while ((p = strsep(&options, ",")) != NULL) {
                int token;

                if (!*p)
                        continue;

                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_kmsg_bytes:
                        if (!match_int(&args[0], &option))
                                pstore_set_kmsg_bytes(option);
                        break;
                }
        }
}

/*
 * Display the mount options in /proc/mounts.
 */
static int pstore_show_options(struct seq_file *m, struct dentry *root)
{
        if (kmsg_bytes != CONFIG_PSTORE_DEFAULT_KMSG_BYTES)
                seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
        return 0;
}

static int pstore_remount(struct super_block *sb, int *flags, char *data)
{
        sync_filesystem(sb);
        parse_options(data);

        return 0;
}

static const struct super_operations pstore_ops = {
        .statfs         = simple_statfs,
        .drop_inode     = generic_delete_inode,
        .evict_inode    = pstore_evict_inode,
        .remount_fs     = pstore_remount,
        .show_options   = pstore_show_options,
};

static struct dentry *psinfo_lock_root(void)
{
        struct dentry *root;

        mutex_lock(&pstore_sb_lock);
        /*
         * Having no backend is fine -- no records appear.
         * Not being mounted is fine -- nothing to do.
         */
        if (!psinfo || !pstore_sb) {
                mutex_unlock(&pstore_sb_lock);
                return NULL;
        }

        root = pstore_sb->s_root;
        inode_lock(d_inode(root));
        mutex_unlock(&pstore_sb_lock);

        return root;
}

int pstore_put_backend_records(struct pstore_info *psi)
{
        struct pstore_private *pos, *tmp;
        struct dentry *root;
        int rc = 0;

        root = psinfo_lock_root();
        if (!root)
                return 0;

        mutex_lock(&records_list_lock);
        list_for_each_entry_safe(pos, tmp, &records_list, list) {
                if (pos->record->psi == psi) {
                        list_del_init(&pos->list);
                        rc = simple_unlink(d_inode(root), pos->dentry);
                        if (WARN_ON(rc))
                                break;
                        d_drop(pos->dentry);
                        dput(pos->dentry);
                        pos->dentry = NULL;
                }
        }
        mutex_unlock(&records_list_lock);

        inode_unlock(d_inode(root));

        return rc;
}

/*
 * Make a regular file in the root directory of our file system.
 * Load it up with "size" bytes of data from "buf".
 * Set the mtime & ctime to the date that this record was originally stored.
 */
int pstore_mkfile(struct dentry *root, struct pstore_record *record)
{
        struct dentry           *dentry;
        struct inode            *inode;
        int                     rc = 0;
        char                    name[PSTORE_NAMELEN];
        struct pstore_private   *private, *pos;
        size_t                  size = record->size + record->ecc_notice_size;

        if (WARN_ON(!inode_is_locked(d_inode(root))))
                return -EINVAL;

        rc = -EEXIST;
        /* Skip records that are already present in the filesystem. */
        mutex_lock(&records_list_lock);
        list_for_each_entry(pos, &records_list, list) {
                if (pos->record->type == record->type &&
                    pos->record->id == record->id &&
                    pos->record->psi == record->psi)
                        goto fail;
        }

        rc = -ENOMEM;
        inode = pstore_get_inode(root->d_sb);
        if (!inode)
                goto fail;
        inode->i_mode = S_IFREG | 0444;
        inode->i_fop = &pstore_file_operations;
        scnprintf(name, sizeof(name), "%s-%s-%llu%s",
                        pstore_type_to_name(record->type),
                        record->psi->name, record->id,
                        record->compressed ? ".enc.z" : "");

        private = kzalloc(sizeof(*private), GFP_KERNEL);
        if (!private)
                goto fail_inode;

        dentry = d_alloc_name(root, name);
        if (!dentry)
                goto fail_private;

        private->dentry = dentry;
        private->record = record;
        inode->i_size = private->total_size = size;
        inode->i_private = private;

        if (record->time.tv_sec)
                inode->i_mtime = inode->i_ctime = record->time;

        d_add(dentry, inode);

        list_add(&private->list, &records_list);
        mutex_unlock(&records_list_lock);

        return 0;

fail_private:
        free_pstore_private(private);
fail_inode:
        iput(inode);
fail:
        mutex_unlock(&records_list_lock);
        return rc;
}

/*
 * Read all the records from the persistent store. Create
 * files in our filesystem.  Don't warn about -EEXIST errors
 * when we are re-scanning the backing store looking to add new
 * error records.
 */
void pstore_get_records(int quiet)
{
        struct dentry *root;

        root = psinfo_lock_root();
        if (!root)
                return;

        pstore_get_backend_records(psinfo, root, quiet);
        inode_unlock(d_inode(root));
}

static int pstore_fill_super(struct super_block *sb, void *data, int silent)
{
        struct inode *inode;

        sb->s_maxbytes          = MAX_LFS_FILESIZE;
        sb->s_blocksize         = PAGE_SIZE;
        sb->s_blocksize_bits    = PAGE_SHIFT;
        sb->s_magic             = PSTOREFS_MAGIC;
        sb->s_op                = &pstore_ops;
        sb->s_time_gran         = 1;

        parse_options(data);

        inode = pstore_get_inode(sb);
        if (inode) {
                inode->i_mode = S_IFDIR | 0750;
                inode->i_op = &pstore_dir_inode_operations;
                inode->i_fop = &simple_dir_operations;
                inc_nlink(inode);
        }
        sb->s_root = d_make_root(inode);
        if (!sb->s_root)
                return -ENOMEM;

        mutex_lock(&pstore_sb_lock);
        pstore_sb = sb;
        mutex_unlock(&pstore_sb_lock);

        pstore_get_records(0);

        return 0;
}

static struct dentry *pstore_mount(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data)
{
        return mount_single(fs_type, flags, data, pstore_fill_super);
}

static void pstore_kill_sb(struct super_block *sb)
{
        mutex_lock(&pstore_sb_lock);
        WARN_ON(pstore_sb && pstore_sb != sb);

        kill_litter_super(sb);
        pstore_sb = NULL;

        mutex_lock(&records_list_lock);
        INIT_LIST_HEAD(&records_list);
        mutex_unlock(&records_list_lock);

        mutex_unlock(&pstore_sb_lock);
}

static struct file_system_type pstore_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "pstore",
        .mount          = pstore_mount,
        .kill_sb        = pstore_kill_sb,
};

int __init pstore_init_fs(void)
{
        int err;

        /* Create a convenient mount point for people to access pstore */
        err = sysfs_create_mount_point(fs_kobj, "pstore");
        if (err)
                goto out;

        err = register_filesystem(&pstore_fs_type);
        if (err < 0)
                sysfs_remove_mount_point(fs_kobj, "pstore");

out:
        return err;
}

void __exit pstore_exit_fs(void)
{
        unregister_filesystem(&pstore_fs_type);
        sysfs_remove_mount_point(fs_kobj, "pstore");
}